How often do you dose your dog Ivermectin for demo mange?

I tried it once a week and it worked for 4 weeks then the hair started falling out and continued after 3 more weeks of dosing. I've read where it's once a day dosing but my vet said to try every 4 days because its toxic...Advice? I've used Mitaban, Goodwinol.....and now Ivermectin